1. Field of the Invention
The present invention relates generally to an optical connection terminal for use in a fiber optic communications network, and more particularly, to an overmolded multi-port optical connection terminal including a tether cable, an overmolded housing, at least one connector port, and plenum means for accommodating excess fiber length (EFL).
2. Description of the Related Art
Optical fiber is increasingly being used for a variety of broadband communications including voice, video and data transmissions. As a result of the increase in demand for broadband communications, fiber optic networks typically include a large number of mid-span access locations at which one or more optical fibers are terminated or “branched” from a distribution cable. The mid-span access locations provide an interconnection point, also referred to herein as a “tap point,” from the distribution cable leading to a network distribution terminal, or from the distribution cable leading directly to an end user, commonly referred to as a subscriber. Connectorized drop cables may be used to connect the subscriber with the network at the tap point, thereby extending an “all optical” communications network to the subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH), or “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.”
In conventional fiber optic networks, drop cables are typically interconnected with a distribution cable at a mid-span access location within an aerial or buried splice closure. Substantial expertise and experience are required to enter the splice closure and initially install, reconfigure or repair the optical fiber connections within the closure. In particular, it is often difficult to access the splice closure and to identify the optical fibers of the distribution cable to be interconnected with a particular drop cable. Once identified, the optical fibers of the distribution cable are typically joined directly to the optical fibers of the drop cables at the mid-span access location using conventional fusion or mechanical splicing techniques. In other instances, the optical fibers of the distribution cable and the optical fibers of the drop cables are first spliced to a short length of optical fiber having an optical connector attached at the other end, referred to in the art as a “pigtail.” The corresponding pigtails are then connected to opposite sides of an adapter to interconnect the drop cables with the distribution cable. In either case, the process of entering the splice closure is not only time consuming, but must be accomplished by a highly skilled field technician at a significant cost and under field working conditions that are usually less tan ideal. Reconfiguring a splice closure is especially difficult, particularly in applications where at least some of the optical fibers of the distribution cable extend uninterrupted through the closure. In such instances, the splice closure cannot be removed from the distribution cable to reconfigure the optical fiber connections. Further, once the connections are made, it is often difficult to subsequently re-route the connections or to add additional connections.
In order to reduce costs and allow less experienced field technicians to more easily perform field connections, optical connection terminals have been developed that include a length of tether cable having optical fibers on one end that are optically connected to optical fibers terminated from the distribution cable at a mid-span access location and a plurality of connector ports at the other end for receiving connectorized drop cables. These terminals typically include a rugged molded or metal housing defining a cable opening for receiving the tether cable and an internal cavity for separating and routing the optical fibers of the tether to their respective connector ports. Each connector port typically includes a receptacle for readily connecting an optical fiber of the connectorized drop cable to an optical fiber of the tether cable that is spliced to an optical fiber terminated from the distribution cable. The optical connection terminal may be attached to the mid-span access location in the factory or may be added to the mid-span access location in the field subsequent to deployment of the distribution cable. Optical connection terminals including a large number of connector ports, for example eight or twelve, are typically added after cable deployment due to their relatively large size, and thus, their inability to be pulled through small diameter ducts or over aerial installation pulleys.
Although existing optical connection terminals provide convenient access to the terminated optical fibers of the distribution cable, several disadvantages remain. For instance, it is expensive to provide optical connection terminals having a customized number of connector ports using molded or metal housings. Since it is not cost effective to produce optical connection terminals with only the exact number of connector ports needed, connector ports are often left unoccupied, resulting in additional materials costs and sealing requirements. In addition, molded plastic or metal housings defining an internal cavity are difficult to seal at the cable opening, the connector ports and along the mating lines of the parts due to cable shrinkage, cable movement and freeze/thaw cycling. One example of an optical connection terminal is described in U.S. Pat. No. 5,892,870 (the '870 patent) issued to Fingler et al. and entitled Fiber Optic Cable Connector. The '870 patent describes a hollow housing filled with an adhesive that encases the fibers of a multifiber optical cable within the housing to inhibit movement of the cable and the fibers within the housing. Although adequate sealing is achieved, the housing of the '870 patent does not accommodate for excess fiber length (EFL) caused by cable shrinkage or by pistoning that occurs when a connectorized drop cable is mated to a connector port.
Accordingly, there is a specific and unresolved need for an optical connection terminal adapted for interconnection with a distribution cable in a fiber optic communications network that overcomes the disadvantages described above. Specifically, an optical connection terminal is needed that provides convenient and ready access to the optical fibers terminated from the distribution cable, while accommodating for EFL caused by cable shrinkage and pistoning during connector mating in a sealed enclosure. What is also needed is a low cost, rugged optical connection terminal that can be easily customized to provide any number of connector ports and is capable of mitigating any difference between a pre-engineered span length measurement and the actual span length following deployment of the distribution cable that may arise as a result of a network measurement, cable assembly manufacturing or cable deployment error. What is also needed is a multi-port optical connection terminal that includes a tether cable adapted for interconnection to optical fibers terminated from a distribution cable at one end and for interconnection to a plurality of individual connector ports retained within an overmolded housing at the other end, while accommodating for EFL caused by shrinkage of the tether cable or pistoning when a connectorized drop cable is mated with one of the connector ports.